已知sin(π⼀6+a)=1⼀3,求cos(5π⼀6-a),cos(a+2π⼀3)

2025-01-31 14:59:45
推荐回答(1个)
回答1:

用诱导公式cos(5π/6-a)=cos(π-(π/6+a))=-cos(π/6+a)=+-2√2/3
cos(a+2π/3)=cos(π/2+(π/6+a))=-sin(π/6+a)=-1/3